D. All answers are correct.
The slaves included the captives from war (raids from other regions), debtors of large amounts of money and criminals.
The slaves was vital to the economy of the empire. They carried out the heavy work, served as soldiers, craftsmen, and some served as royal advisers.
Thomas Jefferson used the philosophies of John Locke for the Declaration of Independence. The words "life, liberty, and the pursuit of happiness" was an idea first stated by Lock in the Two Treatises on Government.
